In this study, we identified a previously uncharacterized skeletal satellite cell‐secreted protein, R3h domain containing‐like (R3hdml). Expression of R3hdml increases during skeletal muscle development and differentiation in mice. Body weight and skeletal muscle mass of R3hdml knockout (KO) mice are lower compared to control mice. Expression levels of cell cycle‐related markers, phosphorylation of Akt, and expression of insulin‐like growth factor within the skeletal muscle are reduced in R3hdml KO mice compared to control mice. Expression of R3hdml increases during muscle regeneration in response to cardiotoxin (CTX)‐induced muscle injury. Recovery of handgrip strength after CTX injection was significantly impaired in R3hdml KO mice, which is rescued by R3hdml. Our results indicate that R3hdml is required for skeletal muscle development, regeneration, and, in particular, satellite cell proliferation and differentiation.
In addition to pathogenic autoantibodies, polyclonal autoantibodies with unknown physiological roles and pathogenicity are produced in the body. Moreover, serum antibodies against the proprotein convertase subtilisin/kexin type 9 (PCSK9) protein, which is integral to cholesterol metabolism, have also been observed. PCSK9 was also reported to be associated with insulin secretion and diabetes mellitus (DM). Therefore, we aimed to examine the clinical significance of PCSK9 antibodies (PCSK9-Abs) levels. We measured blood PCSK9-Abs and PCSK9 protein levels in 109 healthy donors (HDs) and 274 patients with DM (type 2 DM: 89.8%) using an amplified luminescence proximity homogeneous assay-linked immunosorbent assay. Subsequently, patients with DM were followed up (mean: 4.93 years, standard deviation: 2.77 years, maximum: 9.58 years, minimum: 0.07 years) to examine associations between antibody titers and mortality, myocardial infarction, stroke onset, and cancer. The primary endpoint of this study was to examine whether PCSK9-Abs can be a prognostic marker for overall mortality among the patients with diabetes. The secondary endpoint was to examine the relationship between PCSK9-Abs and clinical parameters. Although both PCSK9-Abs and PCSK9 protein levels were significantly higher in the DM group than in the HD group (p < 0.008), PCSK9-Abs and PCSK9 protein levels showed no correlation in either group. Mortality was significantly associated with higher PCSK9-Ab levels, but unrelated to PCSK9 protein levels. After investigating for potential confounding factors, higher PCSK9-Ab levels were still associated with increased mortality among the patients with DM. PCSK9-Abs may be a novel prognostic marker for overall mortality in patients with diabetes, and further studies are warranted to verify its usefulness.
IntroductionAutoantibodies against inflammatory cytokines may be used for the prevention of atherosclerosis. Preclinical studies consider colony-stimulating factor 2 (CSF2) as an essential cytokine with a causal relationship to atherosclerosis and cancer. We examined the serum anti-CSF2 antibody levels in patients with atherosclerosis or solid cancer.MethodsWe measured the serum anti-CSF2 antibody levels via amplified luminescent proximity homogeneous assay-linked immunosorbent assay based on the recognition of recombinant glutathione S-transferase-fused CSF2 protein or a CSF2-derived peptide as the antigen.ResultsThe serum anti-CSF2 antibody (s-CSF2-Ab) levels were significantly higher in patients with acute ischemic stroke (AIS), acute myocardial infarction (AMI), diabetes mellitus (DM), and chronic kidney disease (CKD) compared with healthy donors (HDs). In addition, the s-CSF2-Ab levels were associated with intima-media thickness and hypertension. The analyzes of samples obtained from a Japan Public Health Center-based prospective study suggested the utility of s-CSF2-Ab as a risk factor for AIS. Furthermore, the s-CSF2-Ab levels were higher in patients with esophageal, colorectal, gastric, and lung cancer than in HDs but not in those with mammary cancer. In addition, the s-CSF2-Ab levels were associated with unfavorable postoperative prognosis in colorectal cancer (CRC). In CRC, the s-CSF2-Ab levels were more closely associated with poor prognosis in patients with p53-Ab-negative CRC despite the lack of significant association of the anti-p53 antibody (p53-Ab) levels with the overall survival.ConclusionS-CSF2-Ab was useful for the diagnosis of atherosclerosis-related AIS, AMI, DM, and CKD and could discriminate poor prognosis, especially in p53-Ab-negative CRC.
Background: Autoantibodies develop in autoimmune diseases, cancer, diabetes mellitus (DM),and atherosclerosis-related diseases. However, autoantibody biomarkers have not been successfully examined for diagnosis and therapy. Methods: Serological identification of antigens through recombinant cDNA expression cloning (SEREX) was used for primary screening of antigens. The cDNA product was expressed in bacteria and purified. Amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA) was used to evaluate antibody levels in serum samples. Results: Phosphoenolpyruvate carboxykinase 1 (PCK1) was recognized as an antigen by serum IgG antibodies in the sera of patients with atherosclerosis. AlphaLISA showed significantly higher serum antibody levels against recombinant PCK1 protein in patients with DM and cardiovascular diseasebut not in those with acute ischemic stroke, transient ischemic attack, or obstructive sleep apnea syndrome, than in healthy donors. The area under the receiver operating characteristic curve for anti-PCK1 antibodies was 0.7024 for DM. The serum anti-PCK1 antibody levels were associated with age, platelet count, and blood pressure. Anti-PCK1-antibody-positive patients showed significantly lower overall survival than the negative patients. Conclusions: Serum anti-PCK1 antibody levels were strongly associated with DM and weakly but significantly associated with cardiovascular disease. The anti-PCK1 antibody marker is useful for predicting the overall survival of patients with DM.
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